The present invention generally relates to methods of detecting a position on a disk, disk units and disks, and more particularly to a method of detecting a position on a disk which is time-divisionally recorded with a data region and a servo region based on a signal read from the disk, a disk unit which employs such a method, and a disk for use in such a disk unit.
Conventionally, there was a method of detecting a position on a magnetic disk by recording 4 kinds of servo mark patterns in a servo region of the magnetic disk. According to this method, an operation is carried out with respect to reproduced signal waveforms of 2 kinds of servo mark patterns out of the 4 kinds of servo mark patterns reproduced by a head, and the detection on the magnetic disk is detected based on a result of the operation. However, since each position on the magnetic disk is detected based on the reproduced signal waveforms of 2 kinds of servo mark patterns out of the 4 kinds of servo mark patterns, there was a problem in that the utilization efficiency of the servo information is poor. In addition, when the head makes a scan so as to traverse cylinders on the magnetic disk during a seek operation or the like, there was a problem in that it is impossible to accurately detect the position on the magnetic disk.
On the other hand, a method of recording the servo mark pattern in 3 kinds of position regions EVEN1, ODD and EVEN2 in the servo region on the magnetic disk has recently been proposed. When a period of a clock is denoted by T, the servo mark pattern is recorded with a period of 8T (xe2x80x9c10001000xe2x80x9d) as a base so that a phase shifts by 45xc2x0 per 1 cylinder. As a result, it is possible to detect the position on the magnetic disk based on the phase of the servo mark pattern which is reproduced by the head, and the utilization efficiency of the servo information is improved. In addition, even in a case where the head traverses the cylinders on the magnetic disk, it is possible to accurately detect the position on the magnetic disk based on the phase of the servo mark pattern which is reproduced by the head. This kind of method of detecting the position on the magnetic disk is sometimes referred to as a phase demodulation technique.
However, in the proposed method described above, a demodulating circuit with respect to the servo information and a demodulating circuit with respect to the data are provided independently. For this reason, there was a problem in that the circuit scale of the demodulating system becomes large, thereby increasing the cost of the disk unit.
Further, the demodulating circuit with respect to the servo information uses a circuit which is set and reset depending on the servo information reproduced by the head, and is designed to convert a time interval between the setting and the resetting to the position information. As a result, there was another problem in that it is impossible to accurately detect the position on the magnetic disk depending on a scanning speed of the head.
Accordingly, it is a general object of the present invention to provide a novel and useful method of detecting a position on a disk, disk unit and disk, in which the problems described above are eliminated.
Another and more specific object of the present invention is to provide a method of detecting a position on a disk, a disk unit and a disk, which can reduce the circuit scale of a demodulating system and reduce the cost of the disk unit by using a portion of a demodulating circuit with respect to servo information in common with a portion of a demodulating circuit with respect to data, and can always accurately detect the position on the disk regardless of a scanning speed of a head.
Still another object of the present invention is to provide a method of detecting a position on a disk which is time-divisionally recorded with a data region and a servo region based on a signal read from the disk, where the servo region is recorded with a servo pattern having a length of consecutive xe2x80x9c0xe2x80x9ds longer than a length of consecutive xe2x80x9c0xe2x80x9ds existing in the data region, the servo pattern has three or more zones with consecutive xe2x80x9c0xe2x80x9ds, and the method comprises the steps of (a) digitizing the signal read from the disk and slicing at a predetermined level so as to convert the signal into xe2x80x9c0xe2x80x9d or xe2x80x9c1xe2x80x9d, and (b) detecting the servo pattern when two zones with consecutive xe2x80x9c0xe2x80x9ds are detected from information converted by the step (a). According to the method of the present invention, it is possible to correctly detect the servo mark pattern, even when a bit dropout or a data generation source is introduced, thereby preventing an unnecessary read retry operation or the like and improving the access speed.
A further object of the present invention is to provide a method of detecting a position on a disk which is time-divisionally recorded with a data region and a servo region based on a signal read from the disk according to a phase demodulation technique, comprising the steps of variably setting, depending on a seek speed, an integrating interval in which position information is demodulated by integrating a signal read from the servo region. According to the method of the present invention, it is possible to correctly detect the servo mark pattern, even when a bit dropout or a data generation source is introduced, thereby preventing an unnecessary read retry operation or the like and improving the access speed.
Another object of the present invention is to provide a method of detecting a position on a disk which is time-divisionally recorded with a data region and a servo region based on a signal read from the disk according to a phase demodulation technique, comprising the steps of correcting an error between a clock signal and data when reading a Gray code recorded in the servo region by use of the clock signal which is asynchronous to the signal read from the disk. According to the method of the present invention, it is possible to accurately detect the position even during a high-speed seek operation, by varying the integrating interval depending on the seek speed.
Still another object of the present invention is to provide a method of detecting a position on a disk which is time-divisionally recorded with a data region and a servo region based on a signal read from the disk according to a phase demodulation technique, where a servo mark pattern is recorded in three kinds of position regions EVEN1, ODD and EVEN2 in the servo region, and the method comprises the steps of converting a phase of the servo mark pattern in the position regions EVEN1 and EVEN2 into a phase of the servo mark pattern at an approximate center of the position region ODD. According to the method of the present invention, it is possible to prevent a phenomenon in which the clock signal and the data gradually become asynchronous when a long signal is read when reading the Gray code.
A further object of the present invention is to provide a disk unit for detecting a position on a disk according to a phase demodulation technique based on a signal read from a disk which is time-divisionally recorded with a data region and a servo region, where the servo region is recorded with a servo pattern having a length of consecutive xe2x80x9c0xe2x80x9ds longer than a length of consecutive xe2x80x9c0xe2x80x9ds existing in the data region, the servo pattern has three or more zones with consecutive xe2x80x9c0xe2x80x9ds, and the method comprises converting means for digitizing the signal read from the disk and slicing at a predetermined level so as to convert the signal into xe2x80x9c0xe2x80x9d or xe2x80x9c1xe2x80x9d, and detecting means for detecting the servo pattern when two zones with consecutive xe2x80x9c0xe2x80x9ds are detected from information converted by the converting means. According to the disk unit of the present invention, it is possible to correctly detect the servo mark pattern, even when a bit dropout or a data generation source is introduced, thereby preventing an unnecessary read retry operation or the like and improving the access speed.
Another object of the present invention is to provide a disk unit for detecting a position on a disk which is time-divisionally recorded with a data region and a servo region based on a signal read from the disk according to a phase demodulation technique, comprising setting means for variably setting, depending on a seek speed, an integrating interval in which position information is demodulated by integrating a signal read from the servo region. According to the disk unit of the present invention, it is possible to accurately detect the position even during a high-speed seek operation, by varying the integrating interval depending on the seek speed.
Still another object of the present invention is to provide a disk unit for detecting a position on a disk which is time-divisionally recorded with a data region and a servo region based on a signal read from the disk according to a phase demodulation technique, comprising correcting means for correcting an error between a clock signal and data when reading a Gray code recorded in the servo region by use of the clock signal which is asynchronous to the signal read from the disk. According to the disk unit of the present invention, it is possible to prevent a phenomenon in which the clock signal and the data gradually become asynchronous when a long signal is read when reading the Gray code.
A further object of the present invention is to provide a disk unit for detecting a position on a disk which is time-divisionally recorded with a data region and a servo region based on a signal read from the disk according to a phase demodulation technique, where a servo mark pattern is recorded in three kinds of position regions EVEN1, ODD and EVEN2 in the servo region, and the disk unit comprises detecting means for converting a phase of the servo mark pattern in the position regions EVEN1 and EVEN2 into a phase of the servo mark pattern at an approximate center of the position region ODD. According to the disk unit of the present invention, it is possible to prevent an erroneous detection of the position during a seek operation by using a head moving speed when demodulating the servo information.
Another object of the present invention is to provide a disk having a position thereon detected according to a phase demodulation technique, comprising a data region and a servo region which are time-divisionally recorded, and a servo pattern having a length of consecutive xe2x80x9c0xe2x80x9ds longer than a length of consecutive xe2x80x9c0xe2x80x9ds existing in the data region, where the servo pattern has three or more zones with consecutive xe2x80x9c0xe2x80x9ds. According to the disk of the present invention, it is possible to correctly detect the servo mark pattern, even when a bit dropout or a data generation source is introduced, thereby preventing an unnecessary read retry operation or the like and improving the access speed.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.